Electron back-scattering patterns in a field emission gun scanning electron microscope

INTRODUCTION.The electron back-scattering pattern (EBSP) is a simple means of obtaining the crystallographic orientation of samples in the SEM. Kikuchi bands are observed on a fluorescent screen ∼15mm in front of a (tilted) sample /l/ and shadows, for example of three spherical balls, can be used to obtain orientation determinations accurate to ± 0. 5° /2/. We have also shown that a fibre-optic detector of angular diameter <2θB can be used to form images of polycrystalline material with markedly increased grain contrast /3/. In the present paper we report that these techniques have been transferred onto an ultra-high vacuum SEM equipped with a field emission gun (FEG). The higher brightness of the FEG enables the spot size to be reduced markedly. The transition between the orientation of one grain and the next has been shown to be as sharp as 50nm. Shifts due to sub-grain boundaries down to ∼1° can be readily seen